[JaZZ]

Mark...

Quote:

Isn't it possible that whatever is being measured here is not "distortion" per se, but the sum total of all the individual components in the signal path in the amp that "colors" the sound with the combined signatures of all those parts? Obviously in addition to the differences in components used, circuit design, power output and other things will affect the sound of one amp vs. another.

...of course there's an interaction of all the components which makes the sound. And of course it's not distortion alone that counts. E.g. the frequency response has a clear impact, but unfortunately it is virtually identical with modern amps. Within the measuring method stereoplay bases its theory on it's the hamonic distortion which is the measuring result, thus the deterioration of the original signal curve and the diverse harmonic distortion products this implies (representing fourier components not present in the source signal).

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Also, just because we have invented 5 or 6 ways of measuring amps performance does not mean that those are the only 5 or 6 metrics that can ultimately be measured that affect sound. The tools available to us at this time for measurement may not be nearly complete enough to capture all that an amp is doing, leading two amps that measure identically to sound completely different.

That's exactly my standpoint too, or should I say «was», in view of the stereoplay theory?

Quote:

In the end, to me, measurements are useful in that they can tell you if an amp has any weird anomolies, but I don't think they're capable of relating how that amp will actually sound to the user.

Agreed. But maybe if the theory finds acceptance, there is a new tool available to evaluate electronic components based on data sheets... (?)

 

[Dusty Chalk]

Quote:

Originally posted by markl Isn't it possible that whatever is being measured here is not "distortion" per se, but the sum total of all the individual components in the signal path in the amp that "colors" the sound with the combined signatures of all those parts?

What's the difference? Distortion == deviance from accuracy. Colouration == deviance from accuracy.

WRT to the rest of your comment, I dont' think you can entirely dismiss a metric, just because you haven't found all of them yet. I do think that this new one is an important one.

 

[bootman]

Did they mention what real and complex "load" they used?
Was it a RC circuit (first order) or an actual speaker load?
(drivers, crossover networks, and enclosure)


My best educated guess (I'm an engineer, but not an audio one)
is that an amp's sound is really dependant on its load.
This will include not only the speakers/headphones but the speaker/headphone cables also.

 

[JaZZ]

bootman...

...they didn't indicate any details to this subject, sorry!

 

[markl]

Quote:

What's the difference? Distortion == deviance from accuracy. Colouration == deviance from accuracy.

Well, what is "accuracy"? "Straight wire with gain"? maybe in the future we will have "componentless" music that appears out of the ether. Until then, we have lots of components in the signal path. two different resistors may measure the same but sound "different". Is that "distortion" or merely the character of the resistor at work, and how do you separate the two? Which one is "accurate" if they both measure the same? Until we have music appearing out of thin air, I would say we'll never know. Obviously, music has to pass through components to be reproduced and heard and measured.
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WRT to the rest of your comment, I dont' think you can entirely dismiss a metric, just because you haven't found all of them yet. I do think that this new one is an important one.

Dusty, I don't dismiss measurements at all. I do dismiss the idea that we've got measurement nailed and we know all the parameters of what makes a particular audio chain sound the way it does.

Mark

 

[Dusty Chalk]

Quote:

Originally posted by markl two different resistors may measure the same but sound "different".

Uh, no, not in my world. If that's the case, then I don't believe we've measured everything about it, yet. I do agree with bootman's comment that it is context-dependent. Quote:

Is that "distortion" or merely the character of the resistor at work, and how do you separate the two?

I think we're having an argument of terminology here. I suspect that you attribute a negative connotation to the term "distortion", with which I do not. I also feel that really mild cases of distortion, such as compression and the euphony introduced by tubes, are still forms of distortion, but for convenience's sake, I usually refer to that type of distortion as "colouration". Quote:

Dusty, I don't dismiss measurements at all. I do dismiss the idea that we've got measurement nailed and we know all the parameters of what makes a particular audio chain sound the way it does.

On that, we agree.

 

[JaZZ]

Normal distortion in amps is not audible as such, but exclusively as coloration (if at all). My own experiments seem to indicate that it's even exclusively euphonic in such homeopathic doses - and, BTW, that the load has very little impact on the sound, at least when it comes to headphones as the complicating factor.

 

[jphone]

Quote:

Originally posted by bootman Did they mention what real and complex "load" they used? Was it a RC circuit (first order) or an actual speaker load? (drivers, crossover networks, and enclosure) My best educated guess (I'm an engineer, but not an audio one) is that an amp's sound is really dependant on its load. This will include not only the speakers/headphones but the speaker/headphone cables also.

This is what I'm trying to point to here. The information is incomplete to pass any judgement. You don't even need a tech background, just common sense.
Quote:

Originally posted by JaZZ bootman... ...they didn't indicate any details to this subject, sorry!

But lacking these "details" the theory is totally reasonable and credible to you.
Quote:

Originally posted by JaZZ Now you miss the point completely. The discussion was about our different «expert» statuses in terms of judging the validity of the stereoplay theory - and not about any personal listening experiences and any deductions therefrom. Your example shows that you would trust an astronomer more when it comes to judge the beauty of star nebula than any layperson...

My understanding was that we were trying to see if the data that you posted supports the theory. I was looking really hard at the graphs and although the colors are beautiful it was really hard to listen to the sound. To be blunt, the way their data is presented, due to their/your fault, is deficient to say the least.

And if being cautious, when the next revolutionary explanation of the differences in amplifiers with incomplete data hits, brands me as "negative" so be it.

And to top it all:

Quote:

Originally posted by JaZZ Normal distortion in amps is not audible as such, but exclusively as coloration (if at all). My own experiments seem to indicate that it's even exclusively euphonic in such homeopathic doses - and, BTW, that the load has very little impact on the sound, at least when it comes to headphones as the complicating factor.

Euphonic and homeo-what?
The load has very little impact on the sound???????!!!!!!!!
I think you are really confused. Do some reading on the subject.

 

[JaZZ]

jphone...

Quote:

But lacking these "details" the theory is totally reasonable and credible to you.

...as to the «complex load»: I really don't care what they used to measure it. They're professionals and know what they have to do to simulate a realistic load or even use an existing speaker. The theory doesn't fall with this detail. Of course the theory is reasonable. Where's the fault? Do you see any? And of course we don't have all information to prove it. There are just four graphs, which serve for nothing but to show the measuring procedure. What's important is in the text. They have not indicated how many amps they have measured and auditioned in this context to come to their conclusion, but I just imply they have gained enough experience to be sure about it. That doesn't imply they're right, of course, but the theory is reasonable and credible.

Quote:

My understanding was that we were trying to see if the data that you posted supports the theory. I was looking really hard at the graphs and although the colors are beautiful it was really hard to listen to the sound. To be blunt, the way their data is presented, due to their/your fault, is deficient to say the least.

What data would you expect? Dozens of graphs? What could they prove better? That there are huge measuring differences in the concerned criteria? So what? You would have to rely on their listening experiences anyway, which «prove» the interrelation between the said distortion patterns and euphonic sound.

Quote:

And if being cautious, when the next revolutionary explanation of the differences in amplifiers with incomplete data hits, brands me as "negative" so be it.

It's not your critical standpoint which makes your contribution «negative», but the lack of any constructivity within your criticism: what's wrong with what?, and the presentation of alternative theories, especially your own preferences. You're appearing as an impersonal person who absolutely refuses to tell anything about the own standpoint and ideology, except for general rejection.

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And to top it all: ... The load has very little impact on the sound???????!!!!!!!! I think you are really confused. Do some reading on the subject.

I even could have said there's no impact... My procedure: I used two sources (CDP and DAC), two headphone amps and various headphones. I was trying to verify the impact of such a low load-impedance as a headphone on the line outs (which «are designed to drive high-impedance loads»). I switched the headphone in parallel to the headphone amp to verify if there's some sound change by plugging it in and out. I really couldn't hear any significant change, except for a very slight volume difference (especially with low-impedance headphones) in the case of my Bel Canto DAC2 (with its 20 ohm output impedance) and a clear volume change in the case of the DVD 963SA (200 ohm). I repeated the same procedure switching two amps in series (the HA-2 as source and the EMP as auditioning amp). Result: no significant sound change at all from the complex load (= the headphone) with the HA-2's output. You're invited to do the same experiment and tell us what you're hearing.

I guess some reading on the subject wouldn't prevent me from hearing what I hear...

Of course I have to admit that in the speaker world the load an amplifier has to do with is even much more complex than with headphones, especially in view of the crossover networks. That's why i have indicated that my experiences and statement are limited to headphones - which are my main concern in this context, due to my «philosophy» regarding the role of headphone amps.

 

[ppl]

this 3D model of testing amps and even claiming that one can predict the sound of Amplifiers with the 3D model is not new and yes it was available in the 1980's. Technics Promoted there new Class A Syncro-Bias Amps of the early 80's with Hp's 3D model and the models are for the most part as shown hear.

 

[lini]

Well, maybe it should be mentioned that (Jo)Hannes Maier's theory in fact isn't that new at all. Actually, the article was just an excerpt or kind of summary for Stereoplay's 25th anniversary edition - the theory itself is ~ 20 years old and regularly got some coverage in Stereoplay since ~ 1985...

Personally, the theory seems plausible to me - but I'd regard that harmonic distortion stuff only as one factor of influence on the sound...

Greetings from Munich!

Manfred / lini

 

[JaZZ]

Manfred...

Quote:

Personally, the theory seems plausible to me - but I'd regard that harmonic distortion stuff only as one factor of influence on the sound...

And which are the other ones?

I'd say you can forget frequency response «curves», because they measure more or less as a straight line with all modern (solid-state) amps. So what's remaining? IM?

One thing I have a problem with is the different bass reproduction* with at the same time identical frequency response (I'd like to see the RKV curve...). I doubt that different harmonic distortion can really cause this. Maybe it's a matter of (frequency-dependent) dynamic behavior? But wouldn't this imperatively affect the harmonic distortion behavior?

(* Of course more bass doesn't necessarily mean better neutrality.)

 

[Dusty Chalk]

Quote:

Originally posted by JaZZ And which are the other ones? I'd say you can forget frequency response «curves», because they measure more or less as a straight line with all modern (solid-state) amps. So what's remaining? IM?

Actually, I wouldn't dismiss accurate frequency response curves so quickly. There is an article in this month's Stereophile in the regional section (under Maryland) about how we distinguish subtle changes in frequency in some cases quite well. Quote:

One thing I have a problem with is the different bass reproduction* with at the same time identical frequency response (I'd like to see the RKV curve...). I doubt that different harmonic distortion can really cause this. Maybe it's a matter of (frequency-dependent) dynamic behavior? ...

Exactly.

And I think it's usually interaction with the amp with the load, is what is usually attributed to amps sounding the most different.

 

[JaZZ]

Quote:

Originally posted by Dusty Chalk Actually, I wouldn't dismiss accurate frequency response curves so quickly. There is an article in this month's Stereophile in the regional section (under Maryland) about how we distinguish subtle changes in frequency in some cases quite well.

O.k., let's leave this open, but I doubt it would cause the same sort of sound differences I have perceived with all amps I owned. BTW, temporarily I have slightly attenuated (~1 dB) the treble with a passive network in the signal path, but the amps' signatures were clearly preserved.

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Exactly.

The problem with the hypothesis of frequency-dependent dynamic behavior is that it should cause different frequency-response curves at different levels. And/or considerable distortions if it implies some signal-shape degradations.

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And I think it's usually interaction with the amp with the load, is what is usually attributed to amps sounding the most different.

At least with (such simple loads as) headphones the load doesn't seem to be of much importance in terms of sonic differences between amps - except for the well-known serial/output impedance issue. It may be of more importance with speakers though.

 

[ppl]

Headphones are indeed quite difficult for the average headphone amp to drive while not exhibiting the magnitude of impedance variation of a multi element loudspeaker thought the Audio range they nonetheless have a unique set of drive requirements all on there own. Most Headphone Amps like loudspeaker Amps have more distortion with the headphones connected than they do into a similar resistive load.

A Dynamic headphone Is a coil of wire and this makes for an inductor that will have a rising impedance vs frequency. the connecting cable is a complex series of capacitors and inductors. when the impedance of the voice coil is greater than the impedance of the cable the complex network of the cable begins to dominate. this can cause an Amp to have poor transient response or oscillate at high frequencies with a load yet remain stable with a pure resistor.

Of paramount impotents is an low output impedance to prevent impedance variations of the load from affecting the frequency response of the transducer. there is a point of too low of an output impedance for the chosen transducer resulting in an over dampened Bass response while this makes for a quick sounding bass it is thin and not musical.

High output current is also required since the Load is made up of complex impedances turning from resistive to capacitive and Inductive depending upon the frequency of transmission. capacitors and inductors are slow to charge and release energy so a larger than normal startup current is required to excite the Network In addition the Amp must handle the return voltage generated by these capacitors and inductors in addition to that also generated by the Voice coil.

then there is the nonlinear distortions like Im (intermodulation) and TIM ( transient intermodulation) that are far more intrusive sonically than the simple harmonic distortion.

Add to these the issues already discussed and it quickly becomes clear that Audio Amplifier design is as much of an Art form as it is science. this is evident by the fact that only a handful of Amplifiers can be called good sounding out of the Hundreds available all claiming technical perfection but sounding dramatically different. IMHO Amplifier design is far more in-depth than mere simulation and measurements will suggest for the time being anyway.